The invention concerns a process for generation of a pulse train of a pulsed-aspirated sterile liquid jet and the pulsed-aspirated liquid jet thus generated to feed a handpiece or a catheter, in particular for surgical and medical applications.
The use of pulsed jets of a sterile liquid under high pressure for surgical purposes is already known.
It is possible, for example, to cite in this regard EP 0636345 in the name of SENTINEL MEDICAL, which concerns a surgical instrument with a pulsed liquid jet for cutting and emulsification along with aspiration for evacuation of the liquid and biological residues.
The pulsed jet is produced by the repeated back and forth motion of an amplifier piston which receives the liquid under depression.
The major disadvantage of this system concerns the use of a piston which can produce only a single pulse train during its working stroke along its path. It is then necessary to refill the piston chamber, a fact which limits this device to discontinuous operation, which is not very compatible with the requirements of the work of surgeons.
There are also inventions associated with eye surgery in which a pulsed liquid jet is directed at the eye, at the cornea in particular, to disintegrate defective tissues and to dislodge deposited or encrusted materials and bodies. These inventions are protected by U.S. Pat. Nos. 3,818,913 and 3,930,505 in the name of WALLACH.
These are high frequency pulsed jets intended for the high repetition rate of disintegration work by a train of impacts for cleaning the crystalline lens by clearing it of defective tissues and foreign bodies and materials. Separate aspiration is provided conventionally for the evacuation of the liquid and residues from the disintegration procedure.
In these last devices, the aspiration is also continuous and separate. In contrast, this is not cutting but rather dislodging and disintegration for the purpose of evacuation of the unwanted tissues and materials.
In general, the high-pressure pulsed liquid jets of the prior art are liquid pulse trains triggered on demand and sprayed onto the dissection zone.
The liquid sprayed is then evacuated by aspiration continuously or when it exceeds a certain quantity deemed to interfere with the continuation of the dissection work.
In these implementations, the surgeon cannot approach the tissue to be dissected too closely with the end of the handpiece because of lateral spraying of liquid and the splattering thus generated interfering with the visibility of the operative field.
Moreover, the dissection yield is only slightly better than that with a continuous jet because of the rebound phenomena.
And finally, the penetration of liquid, even though it is sterile, into the incision in small but non-negligible quantities is a disadvantage for the body of the patient, which must eliminate it in addition to all the other stresses associated with the surgery.
The object of the present invention is to remedy the aforementioned disadvantages by proposing a process for generation of a pulsed train of a pulsed-aspirated sterile liquid jet and the pulsed-aspirated jet thus generated to feed a handpiece, a catheter, or the like, intended for surgical or medical applications.
According to the basic process, the firing of elementary pressurized liquid jets is periodically controlled by opening and cutting the flow of the pressurized liquid feeding the handpiece periodically at a repetition rate FR. The on and off aspiration is controlled at the same repetition rate at times such that the firing occurs during aspiration, with the cutoff of the aspiration occurring before the next periodic control of the firing of the pressurized liquid jet. This process enables creation of a jet ejected and aspirated with high surgical effectiveness.
To this end, the basic process according to the invention is characterized in that a pressurized liquid channel, under high pressure, for example, and a pneumatic aspiration channel are used and in that the firing of the pressurized jet is controlled periodically during the periodic application of the aspiration and in that the tissue is released during the interruption of the aspiration by aeration.
The process according to the invention presents numerous advantages.
It enables avoiding lateral spraying and splashing of any type and because of this, it offers good visibility of the operative field at the same time as the possibility of very closely approaching the tissue to be incised.
Since it is a pulsed-aspirated jet, i.e., a jet fired at the same time as the aspiration is operating, the tissue remains taut, i.e., tight momentarily before and during the firing at the end of the sheath on the end of the handpiece, then relaxes during the final phase of aspiration. Thus, one fires at tight tissue, which ensures precision and cleanness of the incision and of the operative field.
Since the period of application of the jet is short, low consumption of sterile liquid is guaranteed.
During specific phases of the surgical intervention, or for specific applications, it is advantageous to increase the repetition rate of the pressure jet.
However, when the repetition rate of the jet increases, and/or when, after a certain length, the inertia, the elasticity, and the reservoir effect associated with the distortion of the feed tube of the handpiece and the residual pressure become perceptible, this basic procedure becomes less efficient.
In effect, despite the presence of a reinforcing sheath, the high-pressure liquid feed tube becomes slightly distorted. The decaying edge of the pressure pulse does not merely slope but becomes rounded, permitting the appearance of an inefficient zone increasing with the pulse rate which encroaches on the recovery and aspiration zone, such that, beginning with an upper limit of frequencies, one approaches a continuous pattern, losing the advantages associated with the pulsed pattern.
However, the existence of a high-pressure cutting edge which is clean, steep, and of short duration is an important condition for precision, convenience, and efficiency in surgical work.
The object of the variant of the basic process is to remedy these disadvantages.
The inventive principle of this variant consists in obtaining a decaying edge of the pressure pulses of the liquid jet no longer only by cutting the pressure and thus cutting the jet, but rather by establishment of simultaneous or quasi-simultaneous communication of the liquid feed line with the exterior, in particular with the air or with the aspiration or with the vacuum generator.
According to the variant of the basic process, as an offshoot on the pressurized liquid feed tube, a branch line connected to the depression generator or to the air via an opening and closing element controlled at the repetition rate in sync with the other controls is provided in order to discharge the residual pressure existing in the pressurized liquid feed line before the next firing. This periodic control of establishment of communication of the pressure line with the exterior occurs simultaneously or immediately before or after the cutoff command of the high-pressure feed line.
This variant of the process presents various additional advantages:
trailing edge of the pressure pulse marking the very steep termination when the repetition rate increases;
efficiency and cleanness in the surgical work;
an improvement very easy to implement.